In recent years, color photographic material makers have proceeded with development of photographic materials which have high sensitivity and can produce images of high quality, and thereby have supplied users' needs.
To enhance image quality, improvements in graininess, sharpness and color reproducibility have been carried out. As an effective measure for such improvements, it is already known to incorporate into a photographic material compounds of the kind which can release a development inhibitor or a precursor thereof in proportion to the image density at the time of development.
Representative compounds of that kind are the DIR compounds and the DIR couplers disclosed, e.g., in U.S. Pat. Nos. 3,148,062, 3,227,554, 3,379,529, 3,615,506, 3,617,291, 3,632,345 and 3,639,417, JP-A-49-129536 (U.S. Pat. No. 3,930,863), JP-A-51-6724 (U.S. Pat. No. 4,063,950), JP-A-62-166334 and JP-A-63-37346 (U.S. Pat. No. 4,861,701) (The term "JP-A" as used herein means an "unexamined published Japanese patent application"). The characteristic effect of such compounds consists in making it feasible to improve sharpness of images through reduction of the size of image grains and through an edge effect. Such compounds also make ti posibble to improve color reproducibility through an interlayer effect, and they make it possible to control the image tone.
Since such a compound can release a development inhibitor or a precursor thereof only after a reaction with an oxidation product of a developing agent in the development step, it can be easily imagined that the diffusibility of a developing agent into a photographic material and the reactivity between the compound and the oxidation product of the developing agent have a great influence upon image quality. However, it is still a difficult subject to illuminate details and improvements are made mostly by trial and error.
As for the compounds usable as color developing agents, a great number of proposals to use paraphenylenediamines, especially N,N-dialkyl-p-phenylenediamines, have so far been subjected. Such proposals are cited in detail in JP-A-03-246542.
Of the compounds proposed, 4-amino-3-methyl-N-ethyl-N-.beta.-hydroxyethylaniline and 4-amino-3-methyl-N-ethyl-N-.beta.-methanesulfonamidoethylaniline are the color developing agents in prevailing use at present.
As for the art of providing silver halide color photographic materials having not only high sensitivity but also excellent graininess and sharpness, the use of tabular silver halide grains having an aspect ratio (or the ratio of the diameter to the thickness of each grain) of at least 8:1 has been proposed, e.g., in JP-A-58-113934 (U.S. Pat. No. 4,439,520).
However, tabular silver halide grains have a disadvantage in that they cause a decrease in the interlayer effect. The interlayer effect improves image quality, and when this effect is decreased color reproducibility is lowered. In order to obviate such a disadvantage, the combined use of these tabular silver halide grains and a compound capable of releasing a diffusible development inhibitor has been proposed in JP-A-59-129849 and JP-A-61-14635.
As a result of examining influences of DIR compounds upon the improvement in image quality when compounds other than the prevailingly used 4-amino-3-methyl-N-ethyl-N-.beta.-hydroxyethylaniline and 4-amino-3-methyl-N-ethyl-N-.beta.-methanesulfonamidoethylaniline are used as color developing agents, it has now been found that higher sharpness than has been achieved in the past and an improvement in color reproducibility due to the interlayer effect can be obtained by using the compounds disclosed as color developing agents in British Patent 807,899 and EP-A-0410450.
Further, it has also been found that the use of the foregoing compounds as color developing agents can overcome the disadvantage that an interlayer effect is reduced by the use of tabular silver halide grains.